Name: data-accessor
Version: 0.1.3
License: GPL
License-File: LICENSE
Author: Henning Thielemann , Luke Palmer
Maintainer: Henning Thielemann
Homepage: http://www.haskell.org/haskellwiki/Record_access
Package-URL: http://code.haskell.org/data-accessor/
Category: Data
-- Portability: Haskell98, not quite because of MTL dependency
Build-Type: Simple
Build-Depends: base>=1.0, array, containers, mtl
Synopsis: Utilities for accessing and manipulating fields of records
Description:
In Haskell 98 the name of a record field
is automatically also the name of a function which gets the value
of the according field.
E.g. if we have
.
data Pair a b = Pair {first :: a, second :: b}
.
then
.
> first :: Pair a b -> a
> second :: Pair a b -> b
.
However for setting or modifying a field value
we need to use some syntactic sugar, which is often clumsy.
.
modifyFirst :: (a -> a) -> (Pair a b -> Pair a b)
modifyFirst f r\@(Pair {first=a}) = r{first = f a}
.
With this package you can define record field accessors
which allow setting, getting and modifying values easily.
The package clearly demonstrates the power of the functional approach:
You can combine accessors of a record and sub-records,
to make the access look like the fields of the sub-record belong to the main record.
.
Example:
.
> *Data.Accessor.Example> (first^:second^=10) (('b',7),"hallo")
> (('b',10),"hallo")
.
You can easily manipulate record fields in a 'Control.Monad.State.State' monad,
you can easily code Show instances that use the Accessor syntax
and you can parse binary streams into records.
See @Data.Accessor.Example@ for demonstration of all features.
.
It would be great if in revised Haskell versions the names of record fields
are automatically 'Data.Accessor.Accessor's
rather than plain @get@ functions.
The package @data-accessor-template@ provides Template Haskell functions
for automated generation of 'Data.Acesssor.Accessor's.
GHC-Options: -Wall
Tested-With: GHC==6.4.1 && ==6.8.2
Hs-Source-Dirs: src
Exposed-Modules:
Data.Accessor
Data.Accessor.Basic
Data.Accessor.Container
Data.Accessor.Show
Data.Accessor.Tuple
Data.Accessor.BinaryRead
Data.Accessor.MonadState
Other-Modules:
Data.Accessor.Example